VIEW ARTICLE

Disease Control and Pest Management

Greenhouse Evaluation of the Curative and Protective Action of Sterol-Inhibiting Fungicides against Apple Scab. W. F. S. Schwabe, Visiting professor, Department of Botany and Plant Pathology and the Pesticide Research Center, Michigan State University, East Lansing 48824; A. L. Jones(2), and J. P. Jonker(3). (2)Professor, Department of Botany and Plant Pathology and the Pesticide Research Center, Michigan State University, East Lansing 48824; (3)Research technician, Fruit and Fruit Technology Research Institute, Stellenbosch 7600, South Africa. Phytopathology 74:249-252. Accepted for publication 26 July 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-249.

Etaconazole at 15 μg/ml, 1-[2-(2,4-dichlorophenyl)-pentyl]1H-1,2,4-triazole (CGA 71818) at 25 μg/ml, fenarimol at 37.5 μg/ml, and bitertanol at 125 μg/ml in combination with an adjuvant at 1 ml/L were highly effective in preventing the formation of apple scab lesions on apple leaves when applied up to 72 hr after the onset of infection periods at 15 C. Applications 120 hr after inoculation resulted in the formation of many chlorotic lesions. With bitertanol at 125 and 250 μg/ml and triforine at 234 μg/ml, chlorotic lesions developed if applications were delayed 24 hr or more after inoculation. Production of conidia was almost completely inhibited by all of the sterol-inhibiting fungicides, even when applied 120 hr after inoculation. Inadequate control was obtained with postinfection applications of dithianon. The protective activity of triforine, etaconazole, bitertanol plus adjuvant, fenarimol, and CGA-71818 was found to decrease faster between application and inoculation than that of captan and mancozeb.